In a communications system, the need to synchronize with a frequency is important for operation of, for example, a demodulator. Some communication systems explicitly provide a signal for such synchronization. An explicit approach may consume bandwidth, and in a bandwidth limited environment may not be advantageous. One form of such an approach is to send a pilot signal. This pilot signal may be an unmodulated reference signal.
Other forms of communication allow for recovery of a frequency for synchronization purposes from the received data stream and/or modulated signal. This approach requires less bandwidth, however recovery of the frequency may be more complex. The acquisition of a frequency from such approaches may have a problem when the initial frequency offset is large. There is also a problem in DSSS systems when the phase coherency of a signal is less than the symbol length. That is, a large frequency offset may prevent the receiver from being able to search for the signal by correlating over the length of the transmit symbol period.